1. Field of the Invention
This invention relates to reverse osmosis residential/commercial/business drinking water systems and other water systems.
2. Background of the Invention
The total dissolved solids in residential drinking water can be drastically reduced by the process of reverse osmosis (RO). This is accomplished by forcing water from a normal source, a municipal delivery system or a well, through a membrane. The liquid that passes through the membrane is known as the permeate, while the liquid that does not pass through the membrane is called the brine. The permeate is stored in a pressure tank and the brine is discharged to a waste line.
The relationship between the permeate and the brine is determined by the saturation of dissolved solids in the source water that can vary widely. In an attempt to commercially accommodate this variation, a fixed relationship is preset by a fixed orifice. This orifice typically allots five parts brine to one part permeate as a one-size-fits-all device.
The source of the feed water remains relatively constant and brine is discharged to drain through the fixed orifice at a steady rate.
As the permeate passes through the membrane and into the pressure tank it increases the pressure on the permeate side of the membrane. This in turn lowers the differential pressure which decreases the productivity of the permeate while the brine remains at its constant discharge rate.
Attention is drawn to U.S. Pat. Nos. 3,568,843, 3,616,921 and 3,939,074.
U.S. Pat. No. 5,778,679, at column 2, lines 15 to 31, states:                “In one special case involving reverse osmosis (RO) systems, the build-up of pressure in the tank reduces the efficiency of upstream water purification processes. As those skilled in the art will readily appreciation, the amount of water purified by, for example, an upstream membrane, is a strong function of the pressure drop across the membrane. A good recovery rate (for the purification process) for a residential system would be 25 percent. Since the process is slow and typical recoveries are one gallon per hour, a storage system is needed.        One of the best systems available for the RO application is the diaphragm expansion tank (such as those described in the incorporated references). The drawback is that at 5 psig the recovery rate may be 25% at a supply pressure 60 psig; however, by the end of the storage cycle the tank pressure may be 40 psig with the recovery rate falling to approximately 8 percent (a poor recovery rate).”        